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Decentralization and Disintermediation in Blockchain-Based Marketplaces De Vos, M.A

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Delft University of Technology Decentralization and Disintermediation in Blockchain-based Marketplaces de Vos, M.A. DOI 10.4233/uuid:a4f750b6-5ac5-4709-80c5-71eb71ac7b35 Publication date 2021 Document Version Final published version Citation (APA) de Vos, M. A. (2021). Decentralization and Disintermediation in Blockchain-based Marketplaces. https://doi.org/10.4233/uuid:a4f750b6-5ac5-4709-80c5-71eb71ac7b35 Important note To cite this publication, please use the final published version (if applicable). Please check the document version above. Copyright Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons. Takedown policy Please contact us and provide details if you believe this document breaches copyrights. We will remove access to the work immediately and investigate your claim. This work is downloaded from Delft University of Technology. For technical reasons the number of authors shown on this cover page is limited to a maximum of 10. Decentralization and Disintermediation in Blockchain-based Marketplaces Decentralization and Disintermediation in Blockchain-based Marketplaces Proefschrift ter verkrijging van de graad van doctor aan de Technische Universiteit Delft, op gezag van de Rector Magnificus prof. dr. ir. T.H.J.J. van der Hagen, voorzitter van het College voor Promoties, in het openbaar te verdedigen op woensdag 16 juni 2021 om 17:30 uur door Marinus Abraham DE VOS Master of Science in Computer Science, Technische Universiteit Delft, Nederland, geboren te Sint-Maartensdijk, Nederland. Dit proefschrift is goedgekeurd door de promotor: Prof.dr.ir. D.H.J. Epema promotor: Dr.ir. J.A. Pouwelse Samenstelling promotiecommissie: Rector Magnificus, voorzitter Prof.dr.ir. D.H.J. Epema, Technische Universiteit Delft, promotor Dr.ir. J.A. Pouwelse, Technische Universiteit Delft, promotor Onafhankelijke leden: Prof.dr. A. van Deursen, Technische Universiteit Delft Prof.dr. A.-M. Kermarrec, École polytechnique fédérale de Lausanne, Switzerland Prof.dr. F. Taïani, Université de Rennes 1, France Dr. A. Gervais, Imperial College London, United Kingdom Dr. D.G.J. Bongaerts, Erasmus University Rotterdam Prof.dr. K.G. Langendoen, Technische Universiteit Delft, reservelid Advanced School for Computing and Imaging This work was carried out in the ASCI graduate school. ASCI dissertation series number 420. Keywords: decentralization, disintermediation, electronic markets, e-commerce, blockchain, decentralized exchanges, matchmaking, settlement, fraud, information management, identity management, decentralized finance, trading, money Printed by: Gildeprint B.V., Enschede, The Netherlands Cover by: Martijn de Vos and Jeannet Stoutjesdijk. The cover shows an artistic impression of the TrustChain ledger. Style: TU Delft House Style, with modifications by Moritz Beller https://github.com/Inventitech/phd-thesis-template The author set this thesisA inLTEX using the Libertinus and Inconsolata fonts. ISBN 978-94-6384-225-9 An electronic version of this dissertation is available at http://repository.tudelft.nl/. v Contents Summary vii Samenvatting ix Acknowledgments xiii 1 Introduction 1 1.1 Decentralization in Blockchain-based Markets . 2 1.2 Disintermediation in Blockchain-based Markets . 6 1.3 Aspects of Blockchain-based Marketplaces . 7 1.4 Research Questions . 16 1.5 Research and Engineering Methodology . 17 1.6 Thesis Outline and Contributions. 18 2 ConTrib: Maintaining Fairness in Decentralized Big Tech Alternatives by Accounting Work 23 2.1 Introduction . 24 2.2 Background and Problem Description . 27 2.3 Accounting Work with ConTrib . 29 2.4 Detecting Fraud . 34 2.5 System Architecture . 40 2.6 Implementation and Evaluation . 42 2.7 Applying ConTrib to Address Free-riding at Scale . 49 2.8 Conclusions . 54 3 MATCH: A Decentralized Middleware for Fair Matchmaking In Peer-to- Peer Markets 55 3.1 Introduction . 56 3.2 Towards Decentralized Matchmaking . 58 3.3 System and Threat Model . 59 3.4 The MATCH Protocol . 61 3.5 The MATCH Middleware Architecture . 68 3.6 Experimental Evaluation . 69 3.7 Related Work. 78 3.8 Conclusions . 79 4 XChange: A Universal Mechanism for Asset Exchange between Permis- sioned Blockchains 81 4.1 Introduction . 82 4.2 Related Work and Problem Description. 85 4.3 Solution Outline . 92 vi Contents 4.4 System Assumptions and Threat Model. 99 4.5 The XChange Trading Protocol. 101 4.6 Security Analysis. 104 4.7 Distributed Logging of Trade Records . 106 4.8 Implementation and Evaluation . 110 4.9 Conclusions . 118 5 Internet-of-Money: Real-time Money Routing by Trusting Strangers with your Funds 119 5.1 Introduction . 120 5.2 Problem Description . 121 5.3 Settlement of Traditional Payments . 122 5.4 Our Money Routing Mechanism . 123 5.5 Building Trust using Blockchain Constructs . 125 5.6 System Design of Internet-of-Money . 128 5.7 Experiments and Evaluation . 131 5.8 Discussion . 135 5.9 Related Work. 136 5.10 Conclusions . 137 6 dAppCoder: A Decentralized Marketplace for dApp Crowdsourcing 139 6.1 Introduction . 140 6.2 Problem Description . 141 6.3 DevID: Unified Portfolios for Software Developers . 143 6.4 dAppCoder: Crowdsourcing the Development of dApps . 148 6.5 Implementation and Deployment Trial . 150 6.6 Related Work. 152 6.7 Conclusions . 153 7 Conclusions 155 7.1 Conclusions . 155 7.2 Future Directions. 157 Bibliography 159 Curriculum Vitæ 179 List of Publications 181 vii Summary arketplaces facilitate the exchange of services, goods, and information between in- M dividuals and businesses. They play an essential role in our economy. The standard approach to devise digital marketplaces is by deploying centralized infrastructure, entirely operated and managed by a market operator. In such centralized marketplaces, trusted intermediaries often provide various services to traders, such as managing market infor- mation, processing payments, and providing arbitration services when a dispute arises. Advancements in information technology have challenged the need for both authorita- tive market operators and trusted intermediaries. In particular, blockchain technology is increasingly being applied to deploy digital marketplaces. Blockchain-based marketplaces facilitate trade directly between peers while reducing the dependency on both authorita- tive parties and trusted intermediaries. The role of blockchain in such marketplaces isto replace social trust with cryptographic primitives. This enables the decentralization and disintermediation of different components in digital marketplaces. In the context ofthis thesis, decentralization refers to the concept of delegating decision-making and activities away from a central authority. Disintermediation reduces or removes the involvement of trusted intermediaries when trading on a digital marketplace. This thesis introduces innovative approaches to decentralize and disintermediate all aspects of blockchain-based marketplaces. We first identify the five aspects of blockchain- based marketplaces: information management, matchmaking, settlement, fraud manage- ment, and identity management. We then design, implement, evaluate, and deploy five decentralized mechanisms. Each introduced mechanism focusses on one or two aspects of blockchain-based marketplaces. For each mechanism, we consider feasibility and real- world deployment as crucial requirements for successful adoption. In Chapter 1 we identify and describe the five aspects of blockchain-based market- places. We outline existing approaches that disintermediate and decentralize these as- pects. We then formulate our research questions, describe our research and engineering methodology, and summarize the key contributions of this thesis. In Chapter 2 we introduce a universal accounting mechanism, named ConTrib, to se- curely store information in decentralized applications. With ConTrib, each peer maintains a personal ledger containing tamper-evident records. A record describes an agreement be- tween peers and links to other records. Fraud, the illegitimate modification of a record in one’s personal ledger, is detected by continuously exchanging records and by verifying the consistency of incoming records against known ones. We experimentally show that ConTrib is highly scalable and that fraud can be detected quickly. To highlight the ap- plicability of our work, we perform a two-year deployment trial of ConTrib to address free-riding behaviour in Tribler, our decentralized file-sharing application. We leverage the accounting capabilities of ConTrib for other mechanisms introduce in this thesis. In Chapter 3 we introduce MATCH, a decentralized middleware for fair matchmaking in peer-to-peer markets. MATCH addresses manipulation concerns associated with mar- viii Summary ketplaces under central control, namely the ability by the market operator to prioritize, hide, or delay specific orders. By decoupling the dissemination of potential matches from the negotiation of trade agreements, MATCH empowers end users to make their own educated decisions and to engage in direct negotiations with trade partners. We evalu- ate MATCH with real-world ride-hailing and asset trading workloads. Our experiments demonstrate that MATCH is highly resilient against malicious matchmakers that deviate from a specific matching policy. In Chapter 4 we introduce a universal and decentralized settlement mechanism named XChange. This mechanism enables
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